1. Field of the Invention
This invention relates to a laser diode excitation type solid-stat laser apparatus having laser diodes.
2. Discussion of the Background
The related art includes a solid-state laser apparatus in which a laser rod is excited by incident light from a plurality of laser diodes. Japanese Non-examined Patent Publications No.5-335662 and No.6-252473 disclose a laser diode excitation type solid-state laser apparatus having a solid-state laser medium which is excited by incident light from a plurality of laser diodes for matching the incident light with a Gaussian beam profile.
The solid-state laser apparatus, however, is difficult to maintain because of the difficulty in replacing defective or failed laser diodes. In addition, the laser apparatus has low reliability and is large.
Japanese Non-examined Patent Publication No.5-335663 also discloses the laser diode excitation type solid-state laser apparatus. The laser apparatus disclosed in this publication has a laser rod in which most of the laser diode beams are applied to only one side of the laser rod. Thus, the laser rod has unbalanced thermal distribution
Japanese Non-examined Patent Publications No. 8-70150 and No. 8-250789 each disclose a flash lamp excitation type solid-state laser apparatus. The laser apparatus disclosed in these publications, has a solid-state laser rod which is excited by incident light on the laser rod after reflection on a surface of an oval mirror that includes both the laser rod and the flash lamp.
However, the laser apparatus is difficult to maintain, because the laser rod and the flash lamp cannot be replaced without taking the oval mirror apart. Consequently, the laser apparatus has low reliability. In addition, the laser apparatus is large because the oval mirror includes the laser rod and the flash lamp. Moreover, the flash lamp has a shorter life span than the laser diodes so that the laser apparatus disclosed in these publications has a short life span.
An object of the present invention is to provide a solid-state laser apparatus that is easy to maintain, achieves high reliability, and is small in size. Another object of the present invention is to provide a laser apparatus that has a solid-state laser rod with balanced thermal distribution applied to the circumference of the laser rod by the incident light from the laser diodes.
The present invention provides a solid-state laser apparatus that comprises a condenser mirror, at least one laser diode, and a laser rod. The condenser mirror has a curved cross-sectional shape with first and second foci. The at least one laser diode is arranged at the first focus of the condenser mirror for irradiating light to the laser rod. A central axis of the laser rod is arranged at the second focus of the condenser mirror. Light axes of the light coincide with the direction of the long axis of the condenser mirror.